Promoting grain growth in Ni-rich single-crystal cathodes for high-performance lithium-ion batteries through Ce doping

Abstract

Preparing a high-performance Ni-rich single-crystal cathode for Li-ion batteries is challenging. This is because calcination must be performed at a high temperature to achieve particle sintering; however, Ni-rich layered cathode materials are damaged if calcination is performed at very high temperatures. Therefore, reducing the calcination temperature required for the synthesis of single-crystal cathodes can improve the performance of the cathode. In this study, a Ni-rich single-crystal Li[Ni0.9Co0.05Mn0.05]O-2 (NCM90) cathode was successfully synthesized at a calcination temperature 50 degrees C lower than its optimal calcination temperature by introducing a Ce dopant. Depending on their properties, dopants affect the growth and sintering behaviors of cathode materials during calcination. W prevents the formation of single-crystal particles by retarding the growth and sintering of grains, whereas Ce promotes the formation of single-crystal particles. Leveraging this feature of Ce, a Ce-doped NCM90 cathode was synthesized at a calcination temperature of 800 degrees C; at this temperature, the pristine (undoped) NCM90 cathode remains polycrystalline. The Ce-doped NCM90 cathode delivers an initial capacity of 199.7 mAh g(-1)at 0.1 C; moreover, cycled at 0.5 C, it retains 80.5% of its initial capacity after 100 cycles, demonstrating better cycling stability than a pristine NCM90 cathode. The reduced capacity loss of the Ce-doped NCM90 cathode is due to the protraction of the detrimental H2-H3 phase transition, as revealed by differential capacity analysis, and its superior thermal stability, which is attributed to the presence of Ce.